This study is designed to determine the comparative effectiveness of zidvudine and larnivudine and 3TC versus the better of ddI monotherapy of ZDV/ddl combination, in respect to progression of HIV disease, weight/growth velocity, or development of neurologic or neuro-psychologic complications of HIV infection. In addition, safety and tolerance of 3TC/ZDV will be evaluated in symptomatic children who have not had more than eight weeks of prior ZDV exposure.